Suction box cover for paper making machines



not corrode,

Patented May 23, 1933 UNITED ST TES PATENT orl-lca EDSON R. GRANGER. OF WATIBBUBY, CONNECTICUT, ASSIGNOB TO CH BOHIUK CORPO- BATION OI AMERICA, 01 NEW YORK; N. Y

A COBPOBATION OI DELAWARE SUCTION BOX COVER FOR PAPER MAKING MACHINES No Drawing.

The invention, relates to improvements-in suction box covers for paper making machines, and has for its 0 ject to provide such covers with a contact surface that will will not groove or wear in sec? tions or zones, will not damage the contacting wire or felt, and will not clog, but Wlll maintain a uniformly smooth wear resisting character indefinitely, resulting in a longer life of the parts coacting with the cover, a

higher operating efiiciency of the machine as a whole and a better product.

Suction boxes are trough-like elements, usually rectangular in cross section, fitted with perforated covers and set crosswise of the paper making machine. In the Fourdrinier section of the machine, they are set under the wire, between the table rolls and the couch rolls. In the press section, they are set under the felt just before the latter enters the nip of the presses. In the Fourdrinier section, the suction box pulls water out of the paper pulp on the wire, while, in the press section, it dries the felt, so that the water squeezed out of the paper by the rolls will be more completely absorbed.

The perforated covers of the suction boxes are usually made of wood, although, in the Fourdrinier section, they are sometimes constructed of brass, bronze, or hard rubber. The prime essential of all suction box covers is that they be smooth, as any roughness in the surface of the covers will result in damage to the wire, or to the felt. The prerequisite of smoothness in the surfaces of the covers is frequently diflicult of maintenance, especially in the Fourdrinier section of the machine, as the wire wears grooves in the covers, which, in turn, soon destroy the mesh or cause the wire to wrinkle and, therefore, produce defects in the paper. \Vooden, rubber, or metal covers heretofore used are also subject to a hollowing out action in addition to the grooving, that is to say, there are more or less extensive areas of the cover Application filed December 11, 1931. Serial ll'o. 580,504.

which are worn out below the general surface contour by the action of the elements of the machine in contact therewith. These hollows do not damage the wire or felt, but they have the effect of diminishing the suction where they occur, with a resultant uneven drying of the paper or the felt. With covers of wood or other materials as heretofore used, these various forms of wear are inevitable, and then it becomes necessary to replace the covers and plane the worn ones down to a new smooth surface. In the Fourdriniersection, such replacements are found to be necessary from ten to thirty days. Wooden covers are used generally,

not because they last longer, but because they are easier to lane down and because, when roughened, t ey do not wear the wire as rapidly as metal or rubber.-

I have discovered that the inherent defects of the older types of suction box covers may be obviated by providing the surface of the cover, in contact with the wire or the felt, with a coating of chromium, preferably electrolytically applied. Because of the hardness of chromium, the covers coated therewith are almost completely resistant to wear and outlast the covers heretofore employed indefinitely before they begin to show any evidences of wear, the

- uniformly smooth surface of the chromium.

between the wire or felt and the covers, with the result that the power required to operate the paper making machine is decreased. Likewise, the smoothness and uniformity of 5 the chromium coating causes the felt and the wire to hug the cover more closely, with the result that the suction may be reduced by more than 40% without decreasing the amount of water that is drawn out of the paper or the felt, or, alternatively, if the suction is unchanged, the paper or the felt may be dried more completely. Furthermore, the smoothness and water repellent character of the chromium plating prevents water accumulating thereon and, therefore, obivates the corrosive action of the water on the wire and the disintegrating action on the felt, when the machine is idle. An inherent objection to the wooden covers is that they become covered with a slime, which rapidly disintegrates the wire or felt, when the machine is stopped, and the mixture of slime and Wood fibers tends to accumulate in the perforations of the cover and choke the suction. lVith the chromium-plated covers, there is no possibility of slime collecting thereon and it has been found that there is no tendency whatever of the perforations to clog or step up, but, on the contrary, such perforations remain open and unobstructed.

To sum up, chromium-plated suction box covers are superior to covers heretofore employed, in that they do not wear out or impair the felts or wires mechanically or chemically; the surfaces of the covers remain smooth and unscored indefinitely; they remove water more efficiently; they permit the machine to be operated at a hi her rate of speed than heretofore; and, fina ly, they insure a superior paper product.

It is to be understood that, in practicing the invention, any suitable metal may be employed for the body of the cover and that the chromium coating may be applied in any convenient manner, but, preferably,

the cover is made of brass, suitably perforated, and chromium is deposited thereon in a dense smooth but relatively thin film from a suitable chromic acid plating bath;

0 the composition and temperature of the bath, the current density and the duration of the depositing action being so adjusted by any one skilled in the art as to insure a smooth, uniform deposit of the desired thickness over the entire surface of the cover.

Various changes may be made in the details disclosed in the foregoing description without exceeding the scope of the invention. or sacrificing the advantages thereof.

What I claim is:

1. A suction box cover for paper making machines, comprising a perforated metal plate having a coating of chromium thereon.

2. A suction box cover for paper making machines, comprising a perforated brass plate having a coating of chromium thereon.

3. A suction box cover for paper making machines, comprising a perforated metal plate. having an clcctroileposited layer of chromium thereon. 

